Yao Tong

Abstract： By studying the current situation of domestic subway construction， the problems of traditional subway construction methods are obtained， several new technologies in the field of subway construction in the new period are briefly introduced， and the concept of environmentally friendly engineering construction is introduced， and the concept of engineering construction is introduced. The idea of solving the problems that construction affects the urban environment. In general， the subway construction period mainly has environmental problems such as outstanding vibration and noise effects， severe hydrogeological environmental problems， insufficient groundwater protection measures， and serious waste of water resources. It is recommended to strictly control subway construction time， optimize tunneling construction technology， and promote new Technical research and application， strengthening construction precipitation reuse， strengthening environmental supervision and other means to mitigate its environmental impact.

Key words： Rail transit; Environmental protection; Construction technology

About the Author：Yao Tong（1989-），Male，Instructor，PhD in Woosong University，Research direction： Operation management of urban rail transit .

1 Basic requirements for the sustainable development of rail transit

Urban sustainable development covers the requirements of economic sustainability， social sustainability and environmental sustainability. The same is true for the sustainable development of urban transportation， which requires the full coordination of land use and transportation systems， different transportation modes， transportation planning and construction and transportation management， transportation development and environmental protection， transportation development with the help of transportation strategies， planning， policies， regulations The relationship with resource input can achieve the purpose of meeting the current transportation needs without damaging the ability to meet future transportation needs， supporting the sustainable development of the economy， society and environment and the sustainable development of the transportation system itself. Major cities in developed countries in the world have basically completed the construction of the subway network. Throughout the development of the rail transit system in these cities， it can be found that the level of the network is considered at the planning level， and the rail transit system is fully utilized for the public for different service areas， different equipment， and different operating organization models. Convenience and quality improvement brought by travel; during system reconstruction and expansion of new lines， the original lines will be fully utilized to improve the system facilities and equipment on the basis of existing ones， as much as possible to reduce the number of Environmental damage and waste of resources. Based on the above basic requirements for urban sustainable development and sustainable development of urban transportation and the rail transit development experience of internationally developed cities， it can be considered that the sustainability of urban rail transportation should involve three requirements： First， it has social sustainability and can improve The service level of the entire city's transportation improves people's travel conditions; the second is environmental sustainability， which can control the negative impact of its development on the ecological environment as much as possible; the third is economic sustainability and accurate positioning of rail transit The nature of the industry， while ensuring its social service function， pays attention to the effective use of resources and reflects the role it can play in economic development.

2 Promote environmental protection and economical subway construction technology

The characteristics of traditional subway excavation construction technology will not be described in detail. China's subway tunnel construction has a history of nearly 40 years. With the arrival of the 2008 Olympic Games， engineers are required to further develop environmentally friendly and economical underground construction technology for the city. Metro tunnel construction opens up new ways. （1） Modern trenchless construction technology. The technology emerged from developed countries， derived from geotechnical drilling technology and gradually developed and matured. It refers to a high-tech， practical， and environmentally-friendly new technology that uses the technical means of geological engineering to lay various underground public facilities without digging the ground. The traditional excavation construction technology has a great disturbance to the normal living order of the residents， which is manifested in the destruction and adverse effects on traffic， environment， and surrounding building foundations. Residents' health caused great damage. Trenchless construction works without grooves on the surface， does not block traffic， and does not destroy the surrounding environment of residents' living and working， such as green spaces and vegetation.The application of trenchless construction technology has environmental advantages， especially reflected The amount of excavated material in the backfilling area at the cut trench is reduced， and the interference and delay to the traffic are reduced. Compared with the traditional road construction method， trenchless construction technology has the advantages of significantly improving social and economic benefits. Due to the unprecedented increase in people's awareness of the protection of the ecological environment， the application and development of trenchless technology will have great potential. （2） Strata freezing method. This method is an environmentally friendly construction technology with good water sealing， high strength and good resilience. It is widely used in the field of mine drilling in China. This technology arranges horizontal freezing holes around the tunnel， and circulates low-temperature brine in the freezing holes to freeze the water-bearing formation near the freezing holes to form a frozen curtain with high strength and good sealing， and then use the mining method under the protection of the frozen curtain Carry out tunnel excavation and construction. The freezing curtain plays a role in closing the groundwater and temporary support， and solves the problem of the special soil layer and overlying ground conditions encountered by the tunnel during the shallow burial and dark excavation construction. With the improvement of technology and the trend of low-cost main material market prices， the formation freezing method has gradually become competitive in underground engineering， and it is a new technology to solve water waste， environmental pollution and traffic interference. （3） Construction technology of expanding shield. Expanded shield construction method is to expand the diameter of some sections on the original shield tunnel to meet the needs of building subway stations and installing other equipment. During construction， first remove part of the original lining and excavate part of the surrounding rock in sequence， and build a space that can be equipped with a shield expansion machine as its starting base. With the removal of the lining， the structure， load and stress of the original tunnel will change， so reinforcement measures must be taken in and around the opening of the original tunnel. The diameter-enlarged shield can be excavated after being assembled in the space after removing the lining， which greatly improves the efficiency， accuracy and safety of the shield technology. （4） Construction technology of spherical shield. This construction method is also known as the continuous excavation construction method at right angles. It is mainly used when it is difficult to guarantee the land of the shield shaft or need to make a right-angle turn. The construction methods of the spherical shield are divided into two types： vertical-horizontal and horizontal-horizontal construction. The cutter part of the shield machine is designed as a sphere and can be steered. Longitudinal-horizontal continuous excavation construction is a method of continuously digging down from the ground in a right-angle direction to a predetermined position， turning， and then implementing a horizontal tunnel construction. Using this method can omit the construction of shield shafts and save engineering construction resources. （5） Synchronous laser automatic measurement and guidance technology. At present， the shield tunnels in China mainly use manual measurement， which has a large measurement workload and affects the construction progress. Moreover， it is impossible to know the attitude and deviation of the shield machine in real time， so the construction control is difficult. The construction guidance systems of shield machines and TBMs in the world mainly include ZED， S LS-T and GYRD systems. The laser guidance system can reflect the position and deviation of the shield machine in real time， guide the construction in time， the technology is mature， the operation is simple， and the guidance accuracy is high.

3 Requirements for sustainable development of urban rail transit in China

At present， the rapid development of urban rail transit in China can only truly play its role as the backbone transportation system of the city and promote the sustainable development of the city if it meets the requirements of sustainable development. Based on the above four aspects， the requirements for the development of urban rail transit can be summarized into two levels： theory and method， technology and industry.

3. 1 Perfection of theory and method

With the formation of urban rail transit networks and the increase in passenger traffic， the impact of an accident at a "point" may show a "line" and "plane" spread， resulting in a larger social and Economic losses. Therefore， the importance of safety for China's urban rail transit has become increasingly prominent. It is necessary to scientifically analyze the vulnerability of the urban rail transit system， establish a theory and method of vulnerability analysis， provide a basis for defining the key elements of the network， predict the impact of events， and penetrate vulnerability analysis throughout network planning and design， operation and management. Throughout the process， the disaster resistance of the rail transit system and the ability to respond to attacks are strengthened.

3. 2 Improvement of technology and industry

The realization of "low-carbon environmental protection" and "intelligence" must be based on advanced technology. The energy saving and emission reduction of urban rail transit involves many professional technologies in the fields of operating organizations， vehicle equipment， power supply systems， ventilation and air conditioning systems， new energy， etc. The solution of a series of problems such as noise and vibration depends on continuous technical indicators Monitoring， analysis of test results， etc.， so we need to pay attention to basic research on key technologies and research and development of advanced technologies. The intelligence of urban rail transit is the product of a series of technologies， including hard technologies such as communication technology， signal technology， new energy technology， etc.， as well as soft technologies such as operation organization management and information services. Therefore， on the one hand， we must constantly update hard technologies to improve the level of intelligent control. On the other hand， we must also pay attention to the improvement of soft technology and improve the level of intelligent management and intelligent services.

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AuthorYao Tong ?Work Unit： Sichuan City Vocational College， Longquanyi District， Chengdu， China， Waizhonghonghe Avenue， 610000